The subject invention relates to a surface effect ship and a system of cushion pressurization by forcing a homogeneous mixture of air and gas into a cushion chamber of a surface effect ship to support the ship above a surface.
At the very outset of surface effect ship development, numerous experiments were made to find and establish the methods of cushion pressurization and propulsion. As a result, it has been determined that a fan and a propeller, driven by engines, are the most effective technical means to provide the surface effect ship with required thrust, flow volume and cushion pressure.
See: (1) L. H. Hayward: The History of Air Cushion Vehicles, London, 1963; (2) I. T Everest: Factors Affecting Hovercraft Performance at Low Speed over Water--"Hovering Craft and Hydrofoil", 1964; (3) J. B. Chaplin: The Air Cushion Vehicle Evaluation and Potential--"Naval Engineers Journal", 1966; (4) L. L. Keiler: Hovercraft Research at Royal Aircraft Establishment, Bedford--"Hovering Craft and Hydrofoil", 1967; (5) G. J. Thomson: The Design and Development of Hovercraft Machinery--"Hovering Craft and Hydrofoil", 1967; (6) M. Wilson: SR.N4--The Biggest Yet--"Air Cushion Vehicles", 1967; (7) Jones R. Stanton: The Future Development of Hovercraft--"Aircraft Engineering", 1968.
The U.S. Pat. No. 4,290,500 to Hopkins et al discloses a small surface effect ship with separate machinery, in which one engine drives a fan to feed the air cushion, and the other engine drives a propeller for thrust. The payload of this small ship is low being eroded by relatively high empty weight.
The U.S. Pat. No. 3,467,213 to Walker discloses a surface effect ship with a combined flow system, in which a turboprop engine drives a propeller in a duct, and the flow of air/gas heterogeneous mixture is discharged partly into a cushion zone of the vehicle, and partly is used to provide with a propulsion jet for movement. It has been determined that, to overcome aerodynamical loss in the propulsive duct, the machinery of this type of vehicle must develop extra flow pressure than is necessary to support the vehicle above a surface. Therefore, the low efficiency is the only reason why a combined flow system was not, in principle, taken into consideration for surface effect ships.
The U.S. Pat. No. 3,302,602 to Korganoff discloses a multipurpose vehicle with a combined flow system, capable of traveling on, below or above the water and above land. Two of many substantial disadvantages of this vehicle will be noted: (1) The engineering value and efficiency of the skirt, usually used to confine the pressurized cushion's chamber, has been simply disregarded, therefore without a skirt, the vehicle must have an enormous source of energy to provide beneath of the ship with required flow volume and pressure for traveling above water and above land. (2) The empty weight of the vehicle's design will be high and, accordingly, the useful load will be low, because the weight of the hull is relatively high, being designed to resist water pressure during traveling under water.
The large and medium operative surface effect ships are equipped with a heavy machinery to transfer the power of the engines to the lift fans and the propellers, to provide with required flow volume, cushion pressure and thrust. The machinery of these ships is heavy, mechanically complicated and consists of many multilink driving shafts, clutches and reduction gears. Typical of such surface effect ships are LCAC, built by Textron Marine Systems, U.S.A., and SR.N6, SR.N4 built by British Hovercraft Corp., Ltd., United Kingdon. In the SR.N4, for instance, driving shafts from the engines to lift fans are 18.3 meters long. Moreover, in accordance with the statistical data, normally there is a substantial loss of energy in the mechanical lift systems of large and medium modern surface effect ships. The loss of energy is between 30% and 35%. Furthermore, the roots of high performance of any vehicle are in its empty weight. The empty weight is the one and only most important index of vehicle's efficiency. The lower is the empty weight, the higher is the vehicle's performance. In other words, the lower is the empty weight, the higher can be the useful load: the payload (a constant load) and the fuel (a variable load).
As is known, the weight problem is best solved in the design of aircraft. On the average, the empty weight of an aircraft is 50% of the gross weight--see JANE'S ALL THE WORLD'S AIRCRAFT, 1985-1986. Typically, the empty weight of a surface effect ship is 60% of the gross weight--see AVIATION WEEK AND SPACE TECHNOLOGY, Mar. 10, 1986. Summary: 1. Two properties characterize desirable high performance of the surface effect ships: their empty weight and the energy losses in the machinery; 2. The principal disadvantages of the large and medium surface effect ships, found in the prior art, are in their relatively high empty weight, and substantial loss of energy in their mechanical lift systems; 3. There has long been a need in the surface effect ships field for a low-cost and high performance ships.